Once the Radiation Oncologist has discussed your treatment plan with you, explaining the objectives and indications for treatment, the treatment activity itself will be simulated in the planning session. During this process, the radiation oncologist and radiation therapist use a CT simulator to locate the exact treatment area on your body and place some preliminary marks on the skin with a marker. These markings made on your skin are very important as they provide the map for administering your treatments. It may be neccessary to pinpoint the area with some small permanent marks, no larger than a freckle.